This application, entitled "Self Renewal and Differentiation of Human Embryonic Stem Cells," is comprised of our Human ES Cell Core Laboratory and 4 Projects. We propose to dramatically expand the work began during our current funding as a University of Washington/Fred Hutchinson Cancer Research Center (UW/FHCRC) "Exploratory Center for Human Embryonic Stem Ceil Research." Our Human ES Cell (hESC) Core Lab, directed by Carol Ware, has acquired and characterized 14 of the 21 NIH approved human ESC lines, and has assisted 18 laboratories in work related to hESCs. The Core will acquire the remaining NIH approved hESC lines, will characterize microRNA expression profiles of all lines, assist all of the component Projects, and will also continue to assist in making hESCs accessible to a local community of more than 80 labs with interests relevant to hESCs. Project 1, led by Blau and Ware, will examine an alternative pathway for self renewal that is activated by the short chain fatty acid, butyrate. Project 2, led by Randall Moon, will examine canonical and non-canonical Wnt signaling pathways in hESCs. Project 3, headed by Charles Murry, examines hESCs during differentiation directed toward a cardiomyocyte fate while Project 4, led by Tom Reh, evaluates directed differentiation toward a neuroretinal fate. Logical and extensive interactions between each of the Projects, and extensive interactions between the hESC Core Lab, each the Projects and other labs at UW/FHCRC create a Program vastly stronger than the sum of its parts.